1. Field of the Invention
This invention relates to the field of discrimination circuits, and particularly to circuits and methods for discriminating between various types of devices that might be plugged into a particular jack.
2. Description of the Related Art
A number of different portable electronic devices might utilize the same type of connector plug to connect to interface circuitry within a separate unit. For example, many stereo headphones and telephone headsets use a common 3-contact plug, which mates with a standard 2.5 mm 3-contact jack as might be found mounted, for example, on a laptop computer, a cell phone, or a CD player. For stereo headphones, two of the plug contacts connect to respective sound transducers and the third plug contact serves as a common ground. For the telephone headset, one plug contact connects to a microphone, one contact connects to a sound transducer, and the third contact serves as a common ground.
Since such devices, referred to herein as “plug-in devices”, share a common plug type, either one might be plugged into a particular jack. In some cases, the interface circuitry connected to the jack is required to accommodate both types of devices. For example, a laptop computer which includes a 2.5 mm 3-contact jack might be required to present a proper interface for either a telephone headset or stereo headphones.
In such cases, it might be desirable for the interface circuitry to know what type of device is plugged into its jack, so that a proper interface can be presented to the plug-in device. This would enable the interface circuitry to be configured properly for the plug-in device, and may avoid damage to the connecting circuitry, the plug-in device, or both.